In the gas utility industry, it is often required that provision be made to detect attempts to tamper with gas meters, said attempts being either for the purpose of removing a meter connection nut to remove a gas blocking plate, or to enable the use of gas directly from the supply line without passing through the meter. For this purpose it has been common to enclose the nut which couples the meter pipe to the supply pipe with a seal in the form of two halves which are fastened together with a lead and wire seal, or are provided with integral means for snapping together into nonremovable engagement. Such a seal is shown in U.S. Pat. No. 4,326,740 and in U.S. Pat. No. 4,372,593.
However it has been found that given sufficient time, an unauthorized person can pick the fastening means in such seals so that the seal can be removed and replaced without leaving evidence of tampering.